Scentry III Battery Back-Up for Gas Shut Off System Is Rechargeable Keeps Pilot Light Lit Battery back-up for Scentry III-GFRAB gas alarm sold separately with gas valve controller capability unit sold separately. Rechargeable battery keeps pilot lights lit during intermittent power failures if no alarm sounds to indicate a gas leak. Scentry III-GFRAB is a versatile home gas detector designed to sense explosive gases like propane gas and natural gas. Options include battery back-up, remote gas sensors and low battery detection. 12V output for phone dialer option to alert owners of vacation homes, etc. when power has flickered or failed at their home. Add up to 4 remote gas sensors near gas ranges, gas water heaters, gas furnaces, gas heaters, etc. to add protection using only one gas valve controller. Note this is the Battery Back Up Only. Scentry III-BB Safety First Battery Back-Up Specifications Case Gray ABS Plastic with physical size 4.625 inches by 4.625 inches x 3.625 Inches Weight 4 lbs Pre-wired for fast installation Power 12V DC, 4.5 AHR Made in USA Manufacturer Safety First USA, Inc. This item ships from a separate warehouse and may require extra time for delivery.